The disclosure concerns an electrographic (in particular an electrophotographic) digital printer to print to a recording medium with toner particles that are transferred from an image carrier onto the recording medium.
Given such digital printers, a latent charge image of an image carrier is inked, for example by means of electrophoresis using a liquid developer. Alternatively, a dry toner may also be applied to the image carrier. The toner image that is created in such a manner is transferred (possibly indirectly via a transfer station) onto the recording medium. Ultimately, the print image is fixed on the recording medium. In the transfer step, an electrical field is used in order to transfer the toner image onto the recording medium.
For a successful and undisturbed (possibly electrophoretic) development step, it is important that the image carrier has a clean, uncontaminated surface. For example, if a developer film remains on the image carrier, flaws in the print image may thus arise. These may be remedied via an external cleaning of the image carrier. However, the image carrier may be mechanically damaged upon its removal and installation.
Alternatively or additionally, as described in DE102009038482A1 a cleaning of the image carrier (in particular of a photoconductor) may take place within the digital printer (for example by means of a cleaning brush). However, should flaws of the print image nevertheless occur, with the system described in DE102009038482A1 it cannot be established whether the flaw of the print image is to be ascribed to a contamination of the image carrier or to another negative effect (for example to a mechanical damage) on the image carrier. The suitable measures to remedy the flaw of the print image thus cannot be directly introduced. JP H11-183390A describes a system with which light that is reflected on a surface may be adjusted uniformly. DE10038399A1 describes a printing system with a reflection sensor to detect defects. EP1271134A1 describes a system to detect defects using scattered light.